I'm using Wolfpack 2s 4200mah 35c
lipo which now puffed up a little.
What to do next.

whats the application ?

I'm using it in my rc car.
With brushed motor and 10A Esc

Find a place to recycle it, rather than throwing it to the dustbin.
Definitely NOT worth the risk of continued use.

What kind of charger are you using?
Is the lipo balanced?

I'm using Imax ac Balance charger.
While balance charging 1st cell voltage rises constantly but the 2nd cell fluctuate with +/- 0.05 volts

Wolfpack packs are very poor quality compared to others like Tattu available locally. Depending on how puffed it is and how bad the low cell is, it is probably safer and better to replace it with a good quality pack.

Which battery is best in quality and cheap in price.

Try Orange Lipos from robu.in, they worked great for me!
Or if your budget allows, then go for graphene packs.

While balance charging 1st cell voltage rises constantly but the 2nd cell fluctuate with +/- 0.05 volts

So what's the problem? Why do you feel the battery is beyond redemption?

From what you describe about the "imbalance" and slight puffing, the battery should be good for another 30 cycles